In this project we seek: to define and classify hereditary tumors of the nervous system in addition to the eight such diseases already recognized; to add to the clinical description and natural history of these diseases; to suggest methods for early diagnosis; evaluate present modes of treatment; and develop methods for preclinical detection and screening. We have documented a central form of neurofibromatosis. In cooperation with several collaborators, we have demostrated distinct alteration in nerve growth factor in blood in affected individuals and approximately half of those at risk.